1. Field of the Invention
The present invention relates to a nitride-based semiconductor device and a method of manufacturing the same.
2. Description of the Background Art
In general, a light-emitting device made of a nitride-based material such as gallium nitride (GaN) has been put into practice as a 405 nm blue-violet semiconductor laser (LD) as a light source for recording/playback employed as a DVD system. A semiconductor laser device emitting blue or green light, employing a nitride-based material has been developed. Such a nitride-based semiconductor laser device is disclosed in each of Japanese Patent No. 2780618 and Japanese Patent Laying-Open No. 11-224866, for example.
A manufacturing process for nitride-based semiconductor chip described in the aforementioned Japanese Patent No. 2780618 comprises steps of forming a pair of dividing grooves opposed to each other on an upper surface of a semiconductor layer and a lower surface of a sapphire substrate in a wafer in which a semiconductor material is stacked on the sapphire substrate, and a step of separating the wafer into chips by dividing the semiconductor layer and the sapphire substrate at portions of these pair of dividing grooves. The pair of dividing grooves are formed by etching or mechanical scribing such as diamond scribing.
A method of manufacturing a laser chip described in the aforementioned Japanese Patent Laying-Open No. 11-224866 comprises a step of dividing a sapphire substrate while forming dividing grooves on a function film and the sapphire substrate by applying a CO2 laser to a wafer where the function film (semiconductor layer) is stacked on the sapphire substrate from a side of an upper surface of the sapphire substrate once or a plurality of times. The sapphire substrate is separated into chips by dividing portions formed with no dividing grooves utilizing thermal stress in laser application in addition to formation of the dividing grooves by the CO2 laser.
In a manufacturing process for the semiconductor chip disclosed in each of the aforementioned Japanese Patent No. 2780618 and Japanese Patent Laying-Open No. 11-224866, however, defects are likely to be caused on the semiconductor layer when forming the dividing grooves because they are formed by etching, mechanically scribing or laser scribing the semiconductor layer which is formed on the substrate by crystal growth. In a case where the nitride-based semiconductor device is the light-emitting device, when the defects reach an emission layer constituting the semiconductor layer, luminous efficiency of the light-emitting device is disadvantageously reduced, and heat is excessively generated in the device following the reduction of the luminous efficiency. In a case where the nitride-based semiconductor device is an electronic device such as a field-effect transistor (FET), abnormal heat is disadvantageously generated due to the defects of the semiconductor layer. Thus, the nitride-based semiconductor device such as the light-emitting device or the electronic device is disadvantageously deteriorated and the life is disadvantageously reduced.